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Colloids and Surfaces. B, Biointerfaces May 2023In this research, CuZnSnS (CZTS) particles were successfully fabricated via the molten salt approach from the copper, zinc and tin sulphides as raw precursors. SEM...
In this research, CuZnSnS (CZTS) particles were successfully fabricated via the molten salt approach from the copper, zinc and tin sulphides as raw precursors. SEM analysis revealed that CZTS particles are tetragonal-shaped with sharp edges, smooth flat plane morphology, and crystal size varying from 10.8 to 28.7 µm. The phase and crystalline structure of synthesized powders were investigated using XRD analysis, which confirms the presence of a tetragonal crystal structure kesterite phase. The chemical composition of CZTS particles was evaluated by EDX spectroscopy, which identified the nearly stoichiometric composition with an averaged formula of CuZnSnS. The TG/DTA-MS and ICP-OES analysis showed the possible decomposition pathways and predicted their degradation rate in aqueous solutions. The CZTS particles possessed highly effective concentration and time-dependent antimicrobial properties against medically relevant bacteria and yeast strains. The CZTS particles (1 g L) exhibited over 95.7 ± 1.9% killing efficiency towards M. luteus. In contrast, higher dosages (3.5 and 5 g L) led to its complete inactivation and reduced the P. aeruginosa cell viability to 43.2 ± 3.2% and 4.1 ± 1.1%, respectively. Moreover, the CZTS particles (0.5 g L) are responsible for causing 54.8 ± 1.8% of C. krusei and 89.7 ± 2.1% of C. parapsilosis yeasts death within the 24 h of exposure, which expanded to almost 100% when yeasts were treated with two times higher CZTS concentration (1.0 g L). The mechanism of action has been proposed and evidenced by monitoring the 2',7'-dichlorofluorescein (DCF) fluorescence, which revealed that the overproduction of reactive oxygen species (ROS) is responsible for microorganism death.
Topics: Anti-Infective Agents; Candida parapsilosis; Cell Survival; Copper; Pseudomonas aeruginosa; Saccharomyces cerevisiae
PubMed: 36965333
DOI: 10.1016/j.colsurfb.2023.113275 -
Food Microbiology Apr 2017With the aim of selecting starter cultures with interesting probiotic potential and with the ability to produce folate in a food matrix, yeast strains isolated from...
With the aim of selecting starter cultures with interesting probiotic potential and with the ability to produce folate in a food matrix, yeast strains isolated from fermented cereal-based African foods were investigated. A total of 93 yeast strains were screened for their tolerance to pH 2 and 0.3% of bile salts. Pichia kudriavzevii isolates gave the best results. Selected P. kudriavzevii strains were tested for survival to the simulated human digestion and for adhesion to Caco-2 cells. Moreover, presence of folate biosynthesis genes was verified and production of extra and intra-cellular folate determined during growth in culture medium. 31% of yeast strains could tolerate pH 2, while 99% bile salts. Survival rate after simulated digestion ranged between 11 and 45%, while adhesion rate between 12 and 40%. Folate production was mainly intracellular, maximum after 24 h of growth. To be closer to traditional cereal-based fermentations, a P. kudriavzevii strain with good probiotic potential was co-inoculated with Lactobacillus fermentum strains in a pearl millet gruel. This resulted in in situ folate production that peaked after 4 h. The use of strains with both probiotic and nutritional enrichment properties may have a greater impact for the consumers.
Topics: Africa; Bile Acids and Salts; Caco-2 Cells; Edible Grain; Fermentation; Folic Acid; Food Microbiology; Food, Fortified; Humans; Limosilactobacillus fermentum; Microbial Viability; Nutritive Value; Pichia; Probiotics
PubMed: 27889145
DOI: 10.1016/j.fm.2016.09.016 -
Journal of Applied Microbiology Feb 2022Isolation, characterization and assessment of inhibitor tolerance of thermotolerant yeasts associated with distillery effluent and molasses, and their use in...
AIMS
Isolation, characterization and assessment of inhibitor tolerance of thermotolerant yeasts associated with distillery effluent and molasses, and their use in high-temperature ethanol production from alkali-treated rice straw.
METHODS AND RESULTS
A total of 92 thermotolerant yeasts were isolated from seven different distillery effluent and molasses samples. Based on MSP-PCR, 34 yeasts were selected and identified by sequencing the D1/D2 domain of LSU rDNA. These yeasts belonged to eight genera and nine different species. We assessed the inhibitor tolerance of these 34 well-characterized yeasts against various pre-treatment-generated inhibitors (furfural, 5-hydroxymethyl furfural and acetic acid) and also evaluated their ethanol yields at 40, 45 and 50℃. Among selected strains, Pichia kudriavzevii DSA3.2 exhibited the highest ethanol production (24.5 g l ) with an efficiency of 95.7% at 40℃ using 5% glucose. At 45℃, P. kudriavzevii DSA3.2 and Kluyveromyces marxianus MSS6.3 yielded maximum ethanol titres; 22.3 and 23 g l with 87.4% and 90% efficiency, respectively. While using alkali-treated RS at 45℃, K. marxianus MSS6.3 produced 10.5 g l of ethanol with 84.5% fermentation efficiency via separate hydrolysis and fermentation, and 10.9 g l of ethanol with 85% efficiency via simultaneous saccharification and fermentation. Pichia kudriavzevii DSA3.2, DSA3.1 and K. marxianus MSS6.3 also exhibited significant tolerance against multiple inhibitors.
CONCLUSIONS
Yeast isolates P. kudriavzevii DSA3.2 and K. marxianus MSS6.3 exhibited significant inhibitor tolerance and proved to be suitable for high-temperature ethanol fermentation. After additional optimization and scale-up experiments, these isolates can be exemplary candidates for industrial-scale ethanol production from lignocellulosic biomass.
SIGNIFICANCE AND IMPACT OF THE STUDY
Our study recognizes distillery effluents and molasses as specialized niches for yeasts with a broad substrate range, capable of tolerating multiple inhibitors and yielding high levels of ethanol at elevated temperatures. These yeasts can further be exploited for bioethanol production through SSF/SHF at a larger scale.
Topics: Bioprospecting; Ethanol; Fermentation; Kluyveromyces; Molasses; Temperature; Yeasts
PubMed: 34487585
DOI: 10.1111/jam.15288 -
Journal of Bioscience and Bioengineering Dec 2020The non-conventional yeast Pichia kudriavzevii is considered to be a promising biotechnological host for the production of organic acids under low-pH conditions....
The non-conventional yeast Pichia kudriavzevii is considered to be a promising biotechnological host for the production of organic acids under low-pH conditions. However, little is known about the low-pH stress response in P. kudriavzevii, which significantly restricts its future development. In this study, P. kudriavzevii N-X showed great tolerance to low-pH stress, but the cell aggregation upon extremely acidic conditions might be unfavorable for low-pH fermentation. We therefore conducted RNA-Seq to compare global gene expression of P. kudriavzevii N-X in response to different pH stresses. Totally 434 genes were identified to be differentially expressed genes (DEGs), and annotation and enrichment analysis suggested that multiple genes associated with regulation of membrane lipid composition, filamentous growth and arginine metabolism were differentially expressed. The increased specific activity of arginase and intracellular ammonia concentration of P. kudriavzevii cultured at pH 2.0 further implied potential roles of arginine in response to extreme low-pH conditions. Extracellular supplementation of 5 mM arginine resulted in increased pHi and cell growth at pH 2.0, meanwhile the cell aggregation was partially suppressed. Additionally, overexpression of ARG J involving in arginine synthesis can also enhance the cell growth and reduce the aggregation effect. These results suggested that increasing arginine flux might be an alternative approach in the developing of P. kudriavzevii as a platform host for production of organic acids under low-pH conditions.
Topics: Arginine; Fermentation; Hydrogen-Ion Concentration; Oxidative Stress; Pichia; Transcription, Genetic
PubMed: 32798135
DOI: 10.1016/j.jbiosc.2020.07.014 -
Journal of Food Science Oct 2022Fungal agents emerged as post-pasteurization contamination are responsible for the spoilage in yogurt drink. In this work, the antifungal effects of some lactic acid...
Fungal agents emerged as post-pasteurization contamination are responsible for the spoilage in yogurt drink. In this work, the antifungal effects of some lactic acid bacteria (LAB) on the spoilage yeasts isolated from yogurt drink (Doogh) were evaluated. First, the microbial growth in the yogurt drink samples during the storage time was investigated, and the isolated microorganisms were identified using biochemical methods and sequencing of the specific amplicons. Yeasts (3-7 log CFU ml ) were found to be the most abundant microorganisms (specific spoilage organisms) in several samples. Using the amplification technique of rDNA by ITS1 and ITS4 primers, the dominant yeasts were identified as Pichia kudriavzevii, Kluyveromyces marxianus, and Candida parapsilosis. Then, the antimicrobial activity of 37 strains of LAB against the isolated yeasts was studied using broth microdilution. Eventually, the strains of Lacticplantibacillus plantarum (245, 24, P6, and P7), Lactiplantibacillus pentosus (20), and Levilactobacillus brevis (30) exhibited significant antifungal activity. In the most effective impacts, lag times of C. parapsilosis, K. marxianus, and P. kudriavzevii were increased by almost 12-19 h, 12-19 h, and 2-6 h, respectively, while the area under the growth curve for these yeasts was reduced to lower than 40%, near 16%, and approximately 67%, in the order given. Overall, these bacteria showed high potential as the substituents for chemical preservatives in yogurt drinks. PRACTICAL APPLICATION: Spoilage yeasts were isolated from yogurt drink and identified by molecular method. Isolated yeasts belonged to Pichia, Kluyveromyces, and Candida genera. Inhibitory effects of 37 strains were evaluated against the spoilage yeasts. Cell-free supernatant was used against the isolated fungi in microdilution method. Several LAB strains showed a significant antimicrobial activity.
Topics: Yogurt; Antifungal Agents; Yeasts; Lactobacillales; Pichia; DNA, Ribosomal; Food Microbiology
PubMed: 36101021
DOI: 10.1111/1750-3841.16305 -
Frontiers in Microbiology 2021Non- yeast with -glucosidase activity might positively contribute to the flavor and quality of wines. The contribution of four non- yeast strains SLY-4, F2-24, F2-16,...
Non- yeast with -glucosidase activity might positively contribute to the flavor and quality of wines. The contribution of four non- yeast strains SLY-4, F2-24, F2-16, and HX-13 with -glucosidase activity to the flavor and quality of wine making was studied. Compared with those of single fermentation, the four non- yeast strains could grow and consume sugar completely with longer fermentation periods, and with no significantly negative effect on chemical characteristics of wines. Moreover, they produced lower content of C compounds, benzene derivative, and fatty acid ethyl ester compounds and higher content of terpene, -ionone, higher alcohol, and acetate compounds. Different yeast strains produced different aroma compounds profiles. In general, the sensory evaluation score of adding non- yeast-fermented wine was better than that of , and SLY-4 fermentation received the highest one, followed by F2-24, F2-16, and HX-13 from high to low. The research results provide a theoretical basis for the breeding of non- yeast and its application in wine making.
PubMed: 34539588
DOI: 10.3389/fmicb.2021.626920 -
AMB Express Nov 2018Food spoilage and its contamination with yeast and mold is a serious problem of food industry. Despite the high fat content, mayonnaise is an attractive substrate for...
Food spoilage and its contamination with yeast and mold is a serious problem of food industry. Despite the high fat content, mayonnaise is an attractive substrate for food spoilage microorganisms. The aim of this study was to develop a method for yeast identification in mayonnaise and to test commercially available mayonnaises for the presence of these contaminating microorganisms. Based on the sequencing of intergenic regions ITS1 and ITS2, we identified a yeast microorganism that causes mayonnaise spoilage. We found that DNA sequences were more than 99% identical to the GenBank DNA sequences from Pichia kudriavzevii. We developed a specific to P. kudriavzevii TaqMan probe and primers. The reaction conditions were optimized regarding to the components concentration and temperature cycle. The minimum amount of P. kudriavzevii DNA that could be detected by developed method was 50 fg. The minimal number of P. kudriavzevii cells that could be detected by developed method without pre-enrichment was 50. We tested verified method with DNAs from microorganisms of different taxonomic groups that were obtained from three collections of microorganisms. Finally, we analyzed 20 different brands of mayonnaise from 14 producers and 10 different brands of mayonnaise sauce from seven producers. We determined the Cq parameter that characterizes transition of the fluorescence curve to the logarithmic phase and, therefore, correlates with the extent of sample contamination with P. kudriavzevii yeast. P. kudriavzevii was detected in six analyzed samples of mayonnaise and one sample of mayonnaise sauce.
PubMed: 30467735
DOI: 10.1186/s13568-018-0716-y -
Food Science and Biotechnology 2017Thermotolerant yeast strains were isolated from , a traditional Korean fermentation starter in which variety of microorganisms are present. Among the isolates, the...
Thermotolerant yeast strains were isolated from , a traditional Korean fermentation starter in which variety of microorganisms are present. Among the isolates, the MBY1358 identified as yeast showed significantly higher growth rate (0.59 ± 0.00 1/h) at 44 °C than other strains. Maximum ethanol concentration of 8.35 ± 0.03 g/L was obtained from 20 g/L glucose with yield of 0.44 ± 0.01 g/g at 44 °C, which is 1.14 times ethanol production of the control strain of . The MBY1358, which was significantly more thermotolerant than the control strain and fermented 200 g/L glucose to 107.33 ± 5.03 g/L ethanol at 44 °C, was deposited to Korean Collection for Type Cultures (KCTC) under the accession number 27654.
PubMed: 30263670
DOI: 10.1007/s10068-017-0155-6 -
Applied Biochemistry and Biotechnology Jun 2024Deoxynivalenol (DON) is a mycotoxin that significantly threatens the food and feed industry. Corn steep liquor (CSL) is an acidic byproduct of the corn starch industry,...
Deoxynivalenol (DON) is a mycotoxin that significantly threatens the food and feed industry. Corn steep liquor (CSL) is an acidic byproduct of the corn starch industry, and DON is concentrated in CSL once the material is contaminated. In this work, a Pichia kudriavzevii strain that could remove DON from CSL was isolated and characterized. The strain P. kudriavzevii E4-205 showed detoxifying activity in a pH range of 4.0~7.0 and temperature of 25~42 °C, and 39.4% DON was reduced by incubating this strain in CSL supernatant diluted by 2-fold (5 μg/mL DON) for 48 h at pH 5.0 and 30 °C. Further mechanism studies showed that P. kudriavzevii E4-205 could adsorb DON by the cell wall and degrade DON by intracellular enzymes with NADH as a cofactor. The degradation product was identified as 3,7,8,15-tetrahydroxyscirpene by liquid chromatography-tandem mass spectrometry. DON adsorption by inactivated cells was characterized, and the adsorption followed pseudo first-order kinetics. This study revealed a novel mechanism by which microbes degrade DON and might serve as a guide for the development of DON biological detoxification methods.
Topics: Trichothecenes; Pichia; Cell Wall; Adsorption; Hydrogen-Ion Concentration; Zea mays; Temperature; Kinetics
PubMed: 37624506
DOI: 10.1007/s12010-023-04712-6 -
Bioresource Technology Nov 2022This study investigated a newly isolated thermotolerant strain of Pichia kudriavzevii with respect to its stress tolerance and fermentation performance. Response surface...
This study investigated a newly isolated thermotolerant strain of Pichia kudriavzevii with respect to its stress tolerance and fermentation performance. Response surface methodology was applied to evaluate the combined effects of furfural, osmotic and thermal stress on ethanol yield. The proposed model shows that P. kudriavzevii has a natural resistance against multiple stress factors. Further evolutionary adaptation of the isolated strain in lignocellulosic hydrolysates improved the ethanol yield by ≥ 24 %. The adapted strain HYPK213_ELA was able to produce ethanol from wheat straw hydrolysates at a high solid loading of 37 %ww at 40 °C and anaerobic conditions. The highest ethanol concentration of 56.8 ± 1.0 gL was reached at 40°C with an inoculum size of 2.5 × 10cellsmL. The results show that Pichia kudriavzevii has the potential to enable high gravity bioethanol production under conditions where most yeast strains are unable to grow.
PubMed: 36220531
DOI: 10.1016/j.biortech.2022.128079